build.js

const fs = require('fs');
const BASE_URL = 'https://taginfo.openstreetmap.org/api/4/key/';
const VALUES_PER_PAGE = 999;
const keys = JSON.parse(fs.readFileSync('keys.json'));

function get_stats(key) {
    return fetch(`${BASE_URL}stats?key=${key}`);
}

function get_values(key, page) {
    return fetch(`${BASE_URL}values?key=${key}&filter=all&lang=en&sortname=count&sortorder=desc&rp=${VALUES_PER_PAGE}&qtype=&format=json_pretty&page=${page}`);
}
function get_key_data(key_to_find) {
    return keys.find(key => key.key==key_to_find);
}

function check_value(key, value, count=false) {
    var allowed_values;
    var key_data = get_key_data(key);
    if(key_data.inherit_from) {
        allowed_values = get_key_data(key_data.inherit_from).allowed_values;
    }
    else {
        allowed_values = key_data.allowed_values;
    }
    if(!allowed_values.includes(value)) {
        if(detected_issues[key][value]) {
            detected_issues[key][value]++;
        }
        else {
            detected_issues[key][value] = (count || 1);
        }
    }
}

function process_value(key, value, count, options={colon_split: false, semicolon_split: false}) {
    if(!options.colon_split && !options.semicolon_split) {
        check_value(key, value, count);
        return;
    }

    var values;
    if(options.colon_split) {
        values = value.split('|');
    }
    else if(options.semicolon_split) {
        values = value.split(';');
    }
    values.forEach(value => {
        if(options.colon_split && options.semicolon_split) {
            value.split(';').forEach(part => {
                check_value(key, part, count);
            });
        }
        else {
            check_value(key, value, count);
        }
    });
}

async function process_page(key, page, options) {
    return get_values(key, page)
    .then(res => res.json())
    .then(res => {
        console.log(`Processing page ${res.page} of ${Math.ceil(res.total/res.rp)} pages for ${key}`);
        res.data.forEach(element => {
            process_value(key, element.value, element.count, options);
        });
    });
}
function generate_keys_data() {
    var keys_copy = JSON.parse(JSON.stringify(keys));
    var res = [];

    keys_copy.sort((a, b) => a.key < b.key);
    keys_copy.forEach(item => {
        if(item.inherit_from==undefined && item.parent_key==undefined) {
            //main tag
            item.subkeys = [];
            res.push(item);
        }
        else {
            //subkey
            res[res.findIndex(main_item => main_item.key==(item.parent_key || item.inherit_from))].subkeys.push(item.key);
        }
    });
    keys_copy.forEach(item => {
        if(item.subkeys && item.subkeys.length==0) {
            delete item.subkeys;
        }
    });
    res.sort((a, b) => a.key < b.key);
    // res.forEach(key => {
    //     if(key.subkeys){
    //         key.subkeys.sort();
    //     }
    // });
    return res;
}
fs.writeFileSync('docs/data/keys.json', JSON.stringify(generate_keys_data()));
var detected_issues = {};

async function run() {
    let promises = [];
    for(const key of keys) {
        if(key.skip_validation) {
            continue;
        }
        if(key.inherit_from) {
            var source = keys.find(a => a.key === key.inherit_from);
            key.allowed_values = source.allowed_values;
            key.colon_split = source.colon_split;
            key.semicolon_split = source.semicolon_split;
        }
        let promise = get_stats(key.key)
        .then(res => res.json())
        .then(stats => {
            var total_pages = Math.ceil(stats.data.find(a => a.type=='all').values / VALUES_PER_PAGE);
            detected_issues[key.key] = {};
            let page_promises = [];
            for(let i1=1;i1<=total_pages;i1++){
                page_promises.push(process_page(key.key, i1, {colon_split: key.colon_split, semicolon_split: key.semicolon_split}));
            }
            return Promise.all(page_promises);
        });
        promises.push(promise);
    }

    Promise.all(promises)
    .then(() => {
        console.log('All data processed');
        fs.writeFileSync('docs/data/detected_issues.json', JSON.stringify(detected_issues));
    });
}

run();